2020 Paper 2

Question 1

Describe how water is treated to make it potable

Answer 1

Pick a fresh water source eg - river. It is then passed through filter beds to remove solids. Then it’s sterilised using chlorine, ozone or uv to destroy harmful microbes

Question 2

What bonds are in alkenes and alkanes

Answer 2

Covalent

Question 3

Suggest one reason why there would only be 2 spots on a chromatogram

Answer 3

Some of the compounds in dye may be colourless

Question 4

What would produce a lower rf value of a new solvent was used

Answer 4

The dye is less soluble in new solvent and more attracted to the new paper

Question 5

Explain why soot is formed in burning of some fossil fuels

Answer 5

If there is incomplete oxygen so incomplete combustion occurs

Question 6

How are oxides of nitrogen produces in car engines

Answer 6

Highly temperature of engine means nitrogen reacts with oxygen

Question 7

Explain ethanoic acid in thus equation is a weak acid

Answer 7

There is incomplete ionisation
on as the reaction is reversible

Question 8

Explain what happens to the mass of the flask as ethanoic aid and zinc carbonate react in it

Answer 8

Mass deceases as carbon dioxide is produced from the reaction and escapes into atmosphere

Question 9

Why is the rate of reaction with metabolic acid greater than rate of reaction with ethanoic acid

Answer 9

Methanoic acid has a lower ph than ethanoic acid (as it’s a stronger acid) and therefore higher concentration of hydrogen Jim’s meaning there is more collisions per unit time with zinc carbonate

Question 10

Unit for rate of reaction

Answer 10

Mol/s

Question 11

Describe shape of dna

Answer 11

Polymer made of of 2 polymer strands sich are made up of 4 monomer chains. They form a spiral called double helix